The ongoing, record-high influx of migrant families crossing into the United States along its southern border has strained U.S. Border Patrol resources so far beyond capacity that, for the first time, the Trump administration's border crisis is spilling out into America's interior.

A senior official at U.S. Customs and Border Protection (CBP) said Friday that federal officials are in the process of identifying locations hundreds of miles from the border that have the capacity to take on some of the arriving migrants, but said no location has been finalized.

"This is an emergency," the official, speaking on the condition of anonymity, said during a conference call with reporters. "The entire system is overwhelmed, and we're simply trying to safely get them out of our custody as quickly as possible while maintaining border security."

CBP officials said they are looking "across the entire nation" for space to house and process migrants before releasing them to await immigration court hearings. A senior Department of Homeland Security official, who spoke on the condition of anonymity, said numerous destinations with government facilities that have the capacity to process migrants are under consideration.

Border Patrol authorities say they have apprehended an average of 4,500 people each day along the southwest border with Mexico, 65 percent of whom are families and unaccompanied children. The number of people in CBP custody recently surpassed 17,500 people - nearly 30 percent more than the agency was detaining when Homeland Security officials declared they had reached a "breaking point" earlier this year.

The Trump administration has said one of its top priorities is to deport MS-13 gang members and other criminals from the interior of the United States, but people apprehended at the border - most of whom are not criminals - are increasingly filling up detention centers this fiscal year, federal records show.

Border crossers account for three-fourths of all migrants booked into immigration custody this fiscal year, up from 61 percent in fiscal 2018, Immigration and Customs Enforcement (ICE) Acting Director Matthew Albence testified earlier this month at a House Homeland Security budget hearing.

The Border Patrol's detention facilities along the border, largely built in the 1980s and 1990s, were constructed for short-term stays and were not designed to accommodate families.

"Our processing cannot keep up with the flow that's coming across, nor can our facilities," the CBP official said Friday.

The Border Patrol, which in recent months began busing migrants from overcrowded facilities in the Rio Grande Valley; El Paso, Texas; and Yuma, Arizona, to other areas of the border, last week took the unusual step of using government aircraft to make some of those transfers.

To make limited transfers of families from the Rio Grande Valley to Del Rio, Texas, and San Diego, California, CBP has been employing aircraft that ICE normally uses for deportations. ICE has contract use of 10 passenger jets, each with a capacity to seat 135 people.

But those locations also are filling up. So CBP has begun "contingency planning" to identify other facilities that can hold them, primarily along the coasts and the 4,000-mile continental border with Canada.

The discussion about transferring thousands of newly detained migrants to cities hundreds of miles from the Rio Grande Valley already is fueling new tensions between the federal government and some local jurisdictions that want nothing to do with the administration's border crisis.

County officials in southern Florida spoke out against the idea Thursday, warning that the transfer of a large migrant population to the region could overwhelm local resources.

Broward County Sheriff Gregory Tony said Friday that he had requested an emergency meeting with county officials after he and another local sheriff's department had learned that CBP was considering releasing "a potential influx of immigrants into both Palm Beach and Broward counties."

Local authorities in Broward and Palm Beach counties said CBP informed them that it was weighing plans to transfer more than 1,000 people a month from the El Paso area of Texas, 1,800 miles away.

"It's insane," Broward Mayor Mark Bogen said in an interview Thursday, noting the impending summer hurricane season and the state's overcrowded homeless shelters. "It's actually inhumane."

CBP said there is no immediate plan to transfer migrants there.

"We do not have any aircraft flying into Florida at this time," the CBP official said Friday. "But we are looking at contingency plans."

Bogen and other local officials said CBP had informed them that border authorities would release many of the migrants into their communities after they had been processed and assigned court dates, standard protocol for migrants encountered at the border.

Most of the families arriving at the southwest border originated in the impoverished and violence-ridden countries of Central America. They often emerge from government holding cells in Texas and Arizona needing food, shelter and medical services - which they often receive from charities and nonprofits that are stationed there.

In Florida, a peninsula where severe hurricanes in recent years have caused significant displacements, officials say they are not set up for a massive influx of migrants in need of housing and other assistance.

"Every day we're watching our border right out here, which is the ocean," Palm Beach County Sheriff Ric Bradshaw said at a news conference Thursday. "We spend a lot of time to make sure that people don't come into South Florida illegally."

Trump in April threatened to release migrants directly into so-called sanctuary cities, an idea that drew internal concerns from the Department of Homeland Security and immediate backlash from Democrats.

Asked whether likely transfer locations included sanctuary cities, the CBP official said: "All we are looking at right now is where we have the capacity and the bandwidth for the computer systems, and the computer systems to be able to do the processing."